Free standing quantum dots (FSQDTs) are semiconductor nanocrystallites whose radii are smaller than the bulk exciton Bohr radius and constitute a class of materials intermediate between molecular and bulk forms of matter. FSQDTs are known for the unique properties that they possess as a result of both their small size and their high surface area to volume ratio. For example, FSQDTs typically have larger absorption cross-sections than comparable organic dyes, higher quantum yields, better chemical and photo-chemical stability, narrower and more symmetric emission spectra, and a larger Stokes shift. Furthermore, the absorption and emission properties vary with the particle size and can be systematically tailored. It has been found that a Cadmium Selenium (CdSe) quantum dot, for example, can emit light in any monochromatic, visible color, where the particular color characteristic of that dot is dependent on the size of the quantum dot.
FSQDTs are easily incorporated into other materials such as polymers and polymer composites because FSQDTs are highly soluble and have little degradation over time. These properties allow FSQDT polymers and polymer composites to provide very bright displays, returning almost 100% quantum yield.
Applications for FSQDT polymers and polymer composites include point of purchase and point of sale posters, mobile device housings or logos, segmented displays, including infrared displays, absorbers for infrared sensors or detectors, and light emitting devices (LEDs). Although the visible advantages inherent to FSQDT polymers and polymer composites are attractive, manufacture of products utilizing FSQDTs are problematic. While solution processable methods and structures exist to enable electrically driven FSQDT emission, such methods are not readily scalable and do not enable patterning of a polymer FSQDT composite on many different types of surfaces.
Thus, what is needed is a scalable method that enables surface-independent patterning of FSQDT polymers or polymer composites. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.